leeds



W. H. ISHERWOOD AND W. H. TURNER.

' ELECTRIC WELDING APPARATUS. APPLICAHON FILED MAR. I3. 1918.

1,318,563. Patented 0ct..14,1919.

lnvenfons ma fi/mJm/Jwrm I PEFMM UNITED STATES PATENT oFrIcE.

WILLIAM HERBERT ISHERWOOD, OF FAR HEADINGLEY, LEEDS, AND WILLIAM HERBERT TURNER. OF LEEDS, ENGLAND. I

Emcmc WELDING APPARATUS.

contact weldigrg, especially for the operation known as spot welding. Hitherto in this kindof apparatus the current is supplied to the primary winding of the welding transformer through a hand or foot-operated switch controlled by the operator, and especially in the case of thin plates or strips, considerable skill and judgment is necessary to produce a satisfactory weld while avoidin injurious excess of current.

ur invention comprises mechanism where- 'by the period during which current is sup "plied is pre-determined, adjustablefor various kinds of work, and independent of the operator.

If the tripping switch makes a suitable number of contacts, diresupplied to the prima".f winding of the transformer instead of thealternating current hitherto used. The E. M. F. is set up in the secondary windingowing to the interruption of the primary circuit'by the tripping switch. i

In the accompanying drawings, the invention is illustrated diagrammatically. The upper electrode a is carried by the a I) rocking about the pivot c and'brou'ght i iito contact with the work or the fixed lower electrode d by means of the connectingrod e operated by the pedal lever f pivoted at 'g.

The electrode a is connectedto one end of the secondary winding h of the transformer by the flexible connection 7'. .The fixed electrode d is carried by a bracket making electrical connection'wlth the other end of the secondary winding h The primary winding 70 of the transformer is connected to the supply mains Z, n through the trippin switch described below, and through a usua form of switch operated by the treadle f. This switch is shown as having two fixed Specification of Letters Patent. 7

if current may be Patented Oct. 14, 1919.

Application filed March'13, 1918. Serial No.- 2223 10.

knife contacts n, 0 which are embraced by the spring contacts p, Q when the latter are raised by the pedal 7.

The tripping switch provided accordingto the present invention consists of a double switch blade 0* with an arm 8 projecting therefrom at right angles. The upper and lower ends of the arm r are adapted to sweep across fixed contacts 25, u, respectively. The arm 8 passes through a stirrup o and is engaged at its rear end by-one of two pawls w, a The connectin rod 6 has fixed to it two laterally projectmg brackets 3 z, and

these'brackets serve to guide two rods 1, 2,

fixed to the stirrup '0. Each of these rodsis encircled by a compression sprin 3, 4.

In operation suppose the wor is placed between the electrodes a, d, and the pedal f'is depressed. The switch n op g is then closed but not before the electrodes are in contactwith the work. This is arranged by a spring device operated by the rod 6 not shown in the drawing. At this stage no current passes because the primary circuit is interrupted between the contacts t, u. Spring 4 however, becomes compressed but cannot operate the switch r owing to the pawl w. However, a pin 5 projecting for-. wardly from the rod 6 ultimately pushes up the tail of the pawl wand allows the switch to be operated. The arm 1- then passes into the dotted position shown in the drawing, during this movement closing the primary circuit for a predetermined time. The switch is locked in the dotted position by the pawl :12.

When the treadle f is released thetop electrodejdis raisedand the switch 'ngo p is opened by the downward movement of ro e, as the parts resume their normal position (by the action of the counterweight m) and at the same time spring 3 is compressed. After switch n 0 p jecting fromback which under the influence of spring 3 re further operation.

is opened, a pin 6 pro rod 0 depresses the tall I of pawl. w and releases the switch blade 1,

Theduration of contact can be varied by means of a dashpot 9- within which is situ} ated a piston 8 having'holes '10 and a valve 11, closed during the upward stroke of the piston 8 by the operation of spring 12 thus retarding the motion of piston 8, extension 7 of rod 2, and the movement of lever and switch blade B. On the downward stroke of rod 2 and piston 8, the valve 11 lifts and permits movement free from retardation of the attached parts.

The blade R however may be varied in Width for this purpose or the same effect may be obtained otherwise.

By arranging the arm- R to make and break one or more contacts, in succession,

which may be effected by providing spaces 13 in the portion of contacts T and U over which the arm R passes, the impulses of direct current which may by this means be admitted to the primary Winding K can enable sufiicient E. M. F. to be induced in the secondary winding to effect the weld in certain cases.

Electric welding machines have been designed in which the movements of the Welder mechanism, the control of the electrical current and in some cases the manipulation of the work to be welded have been efiected by power mechanism and the duration of the flow of current has been dependent upon the driving speed, and out of the control of the operator. Moreover, electric welding machines have also been designed, the operation of which is efiected by electromagnetic means and the duration of current flow determined by a wattmeter relay, so that equal heating effect is obtained by passing equal amloilnts "of electrical energy through each we Our invention relates exclu ively to foot or hand-operated spot welders and We make no claim to mechanically or electrically operated machines.

What we claim is 1. In foot or hand-operated electric spot- Welding apparatus, means for predetermining the duration of current supply independently of the action of the levers which control the articles to be welded, comprising in combination a primary electric circuit, a

right bar in operative connection with said lever, contacts. supported on said bar adapt-- ed to make and break the primary current circuit, a tripping switch adapted to make and break the same circuit, guide rods adapted to control the motion of the tripping switch; and a pair of pawls in operative contact-with the upright bar and adapted to control the opening and closing of the switch.

In testimony whereof We sign our names to this specification in the presence of two subscribing witnesses. a,

WILLIAM HERBERT ISHERWOOD. WILLIAM HERBERT TURNER.

Witnesses:

EDITH M. HOPPER, R. WHEATLEY. 

